Sonos is a pioneer in the wireless audio market — its entire focus is on simple, powerful, high-quality music systems that connect over a home Wi-Fi network, access a huge range of music services, and allow control from a smartphone. The Sonos SUB is the latest addition to the line-up, and is designed to complement existing speakers with extra bass power. See also Group test: what's the best speaker set?

Sonos SUB: Design and setup

The Sonos SUB is, as home entertainment devices go, a Kubrickian monolith. It’s only available in glossy black (a minor upset for any white Sonos system owners), and looks like an oversized, 3D ‘O’ thanks to the silver-trimmed cavity in the centre. Visit Lenco IPD-9000 docking station review.

Inside this cavity are two oval-shaped subwoofer pressure drivers (on the long edge of the ‘O’), facing towards each other. This dual-driver design cancels out any unwanted vibration, so there’s no buzzing cabinet resonance at higher volumes — the end result is clean, untarnished bass at any volume level.

Most users will opt to use the SUB in its standard upright configuration, but it can be placed face-down after four bundled foam feet are attached. This means the SUB can be hidden away underneath a lounge, at the end of a bed, or slotted into a home entertainment unit. The component measures 402 x 158 x 380mm and weighs a hefty 16kg. The supplied AC power cord — yes, that’s all you need to use the SUB — is around 1.5m long.

The only button on the SUB is the Connect button, which you’ll need to press once when you’re mating the component to your pre-existing Sonos speaker setup.

If you’ve already got a Sonos system — which, at minimum, means a BRIDGE wireless bridge and a PLAY:3 orPLAY:5 wireless speaker, but might also include a CONNECT:AMP component and non-Sonos speakers — then setting up the SUB is a breeze.

Open the Sonos app on your smartphone or tablet (or any other Sonos controller device, like a PC or Sonos Control), select the existing Sonos setup, and find the option to add a new component in Advanced Settings. After that you’ve got two minutes to press the SUB’s button — it’ll do the rest automatically. If you’re setting the SUB up along with other Sonos components for the first time, the SUB should be the last thing you install.

We were prompted to install an update after the SUB was connected, and then a quick step-by-step procedure optimised the system for the room we were listening in. A comparison test made sure each speaker driver was outputting at the right power (to prevent any phase problems), then a music listening test let us tailor the volume level against the PLAY:5 speakers that were already set up. That was everything the SUB needed — after that, it’s a seamless part of the Sonos experience.

Sonos SUB: Sound quality and performance

The Sonos SUB is far more gutsy than its relatively compact size suggests. Whether it’s the twin drivers stopping any unwanted resonance, or the outright power of the twin amplifiers, we’re not sure — but pair the SUB with a couple of Sonos speakers and you’ve got a setup that’s able to deliver full, rich and deeply powerful sound in even a large room.

In the medium-sized living room we tested the SUB in, the half-way point on the volume control was more than loud enough for the majority of our listening, with full volume being ear-bleedingly loud. There’s not a hint of distortion even at maximum power, though, and there’s six increments (three positive, three negative) to fine-tune the SUB’s volume.

While there is no resonance from the SUB itself, its low frequency power did a good job of showing up a few annoying rattles in the windows and bookshelves of our test room — this isn’t at all a slight against the SUB, but instead evidence of its impressive power and testament to its excellent build quality.

We tested the SUB with a wide range of music, from classical stalwarts like Beethoven’s 5th Symphony to the electronica of LCD Soundsystem’s Dance Yrself Clean and Kanye West’s Good Morning. There’s absolutely no doubt that everything we listened to benefited from the inclusion of the SUB in our Sonos setup.

A particular stand-out was James Blake’s Limit To Your Love (recommended by Sonos’s local marketing manager) — not only does the SUB effortlessly handle the song’s staccato electronic bass, but adds some warmth to the accompanying piano notes and lets the PLAY:5 speakers handle mid-range and higher frequencies exclusively. Sonos’s PLAY:5 speakers are already impressive for their size, but the SUB blows them away for bass response — we felt like our setup had suddenly become a lot more serious.

Sonos says the SUB is able to extend as far down as 25Hz, making it more than suitable for any music track that could be thrown at it. It’s able to deliver very deep bass kicks with very little decay — the best word to describe the SUB’s output would probably be quick. It’s not an especially boomy subwoofer, with tight response that gives a powerful punch to music rather than drowning out mid-range and treble.

What’s impressive about the SUB is that, once it’s installed, it’s indistinguishable from the rest of the speaker components in a setup. It’s always perfectly in sync, and its bass response is not at all directional. If we hid the SUB and showed the Sonos system to a neighbour, we’d have them scratching their heads as to how two small speakers could produce so much bass.

We tested the SUB with two PLAY setups — one with a single PLAY:5 speaker, and another with two PLAY:5 speakers divided for left and right stereo sound. In both situations, the SUB adds an appropriate and impressive amount of low frequency extension to the full-range speakers, but we found it very slightly better matched to the more spacious sound of the dual-speaker setup.

The SUB will almost certainly be a similarly useful add-on to a dual-PLAY:3 stereo system, but we think it might be a little under-utilised and over-powered for a single PLAY:3 (although you could of course turn it down). Automatic equalisation means the SUB optimises its frequency response to suit whichever PLAY speakers it’s matched to.

As with any subwoofer, the Sonos SUB performs best when it’s working with the speakers it’s been designed to complement. We mostly had it running with two PLAY:5s set up in a stereo configuration, which is probably the best possible setup. If you intend to use it with a CONNECT:AMP and non-Sonos speakers, we’d advise giving it a test run to see if it suits in terms of its bass response and roll-off, and the existing low frequency cross-over of your speakers.

Sonos SUB: Conclusion

The Sonos SUB integrates into existing Sonos systems seamlessly, adds some welcome bass power, and transforms a good audio setup into a great one. We think its £599 retail price is a little expensive, and it does drive up the cost of an already-pricy Sonos setup - but we think it’s well worth it.

Sonos's SUB provides a very welcome low-frequency kick for the already-impressive Play:5 wireless speakers, and the effect would be more pronounced with the smaller Play:3. Seamless integration with an existing Sonos system makes it a very easy upgrade, although it makes an already-pricy audio setup even more expensive.

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